This disclosure relates generally to gas turbine engine exhaust liners. More particularly, the disclosure relates to providing cooling slots in exhaust liners that can be recoated without masking, for example.
Turbojet engines typically include a removable exhaust liner that is secured and supported relative to an exhaust duct. The exhaust liner typically includes hot sheets that are exposed to core exhaust passage. It is desirable to cool surfaces of the hot sheets that face the core exhaust passage to reduce the temperature of the hot sheets. In one example arrangement, the hot sheets include numerous small-diameter holes (up to a quarter million or more) that supply a cooling flow from a bypass flow path to the surfaces.
The hot sheets are typically coated with a thermal barrier material to provide thermal protection to the exhaust liner. This thermal barrier material wears over time. Typically the hot sheets are simply replaced. It is not economical to recoat the hot sheets due to the large number of cooling holes, since all of the holes would need to be plugged or redrilled to ensure that the holes are not obstructed with the thermal barrier material.
In exhaust liner arrangements that use a cold sheet interconnected to the hot sheet, impingement apertures are used to communicate the bypass flow to the cooling holes. The cooling holes, impingement apertures and surrounding structure must be configured such that undesired thermal growth is minimized and the cooling flow is effectively communicated from the bypass flow path to the hot sheet surfaces.
What is needed is an exhaust liner that is recoatable with thermal barrier material and that effectively cools the hot sheets.